Why independent conduit testing is needed

Performance requirements for coated conduit are crucial.


For years, all available brands of polyvinyl chloride (PVC)-coated galvanized conduit met the same UL 6 standards and carried an identical UL label relating to safety conformance. Yet, it was apparent in the marketplace that not all brands performed the same. With products like coated conduit, adhesion of the coating is crucial. If the coating bond is broken, a void is created and moisture penetrates to the metal substrate and corrosion is actually accelerated.

Figure 3: In this polyvinyl chloride (PVC)-coated conduit specimen, the coating adhesion has failed. This conduit sample was exposed for approximately two days in the hot water immersion test. Once the cuts are made, the PVC coating is easily removed by pFigure 4: In this polyvinyl chloride (PVC)-coated conduit specimen, acceptable adhesion is shown. Courtesy: Robroy Industries

The lack of performance requirements for coated conduit has been recognized by many companies and is gaining recognition by users. This fact is confirmed by recent discussions with consulting, specifying, and maintenance engineers at paper plants, wastewater treatment facilities, and other locations. 

Figure 5: Products verified by ETL are clearly labeled. Courtesy: Robroy IndustriesTo confirm the performance of the PVC coating, Intertek evaluated PVC-coated galvanized conduit brands solely for product performance and longevity as tested under conditions consistent with highly corrosive environments. Heat and humidity are recognized corrosion accelerators in corrosion engineering textbooks and technical documents from organizations such as the National Association of Corrosion Engineers (NACE). 

The test results provided a quantitative method to compare the relative performance of coated conduit systems in conditions typical of the corrosive application environments. The results of both tests confirm significant differentiation in adhesion performance of the PVC coated conduit available in the market and why only certain brands carry Intertek’s ETL label.

Stephanie Ellis is director of Corrosion College. She holds a basic certification from the National Association of Corrosion Engineers and is a member of the International Association of Electrical Inspectors. Corrosion College is a hands-on course that explains the process of corrosion through intensive instruction by professionals in the field of corrosion protection.

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